<!DOCTYPE html>
<html lang="en">

	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			* {
				margin: 0;
				padding: 0;
			}
			
			#div1 {
				width: 0;
				height: 0;
				border-left: 10px solid green;
				border-right: 10px solid red;
				border-top: 10px solid yellow;
				border-bottom: 10px solid blue;
				border-radius: 100px;
				position: absolute;
				/*left: 0;
				top: 0;*/
			}
		</style>
		<script>
			document.onmousemove = function(e) {
				var div = document.getElementById("div1");
				div.style.left = e.clientX + "px";
				div.style.top = e.clientY + "px";
			}
		</script>
	</head>

	<body>
		<div id="div1"></div>
	</body>

</html>